1. Field of the Invention
The present invention relates to a radio signal transmission in a cellular base station for a mobile telecommunication system and, more particularly, to a transmission controller for use in the base station capable of simultaneously controlling a multiplicity of radio transmitting signals of the same channel upon transmission.
2. Description of the Related Art
In general, a service area for a mobile telecommunication system is split into a given number of plurality of local sites each provided with a plurality of transmitters in its respective base station for transmitting the radio signals to its subscribers' terminal equipments which are scatteredly located and movable in a very wide area. These transmitters each serve as a kind of interfacing unit of the radio signals in between a central telecommunication system and its subscribers' terminal equipments in every local site via a corresponding base station. Hereinbelow, the mobile telecommunication system is referred to and assumed for instance as a "paging system" for the purpose of better explanation in the present invention.
In a conventional paging system a paging signal is generated by a dialling operation of a telephone subscriber by dialing a predetermined paging number of a desired paging receiver in order to page a given subscriber. The paging signal is then provided to an exchange system which analyzes the paging signal and, if the result of analysis should indicate that a paging receiver is being called, the the paging signal is transmitted to a paging system. The paging system receives the paging signal converts it into a CAP code that is a kind of address codeword for a paging receiver, and transmits the CAP code using POCSAG coding to a transmitter which receives the POCSAG data and converts it into a radio signal for transmission.
The paging system provides a radio paging service for every paging subscriber located within a serviceable area delimited by a plurality of operating cell sites or base stations having a plurality of transmitters. Accordingly, the above-mentioned radio telecommunication system often causes the occurrence of a reiteration cell, that is, an overlapped cell area for the same radio signal between adjacent cell sites, in which case any paging receiver located in such a reiterated cell area may not be provided with the better quality of service of one of the cells. The transmitters are connected with the paging system by a wire or cable, in which a length of each wire or cable is dependent upon the distance between the respective transmitters and the paging system. Therefore, even though each site transmits the same channel of data, the paging signal in the reiterated area is considerably affected by air delay and/or line delay, thereby leading to loss of timing upon transmission of those radio signals, which usually results in a damaged paging signal. The line delay or air delay often causes two adjacent base stations to transmit identical channel data at different times, which makes it substantially impossible to provide an acceptable quality of paging service for any paging receiver located in such a reiterated cell area. For instance, a paging receiver located in the reiterated cell area may fail to receive the paging signal or may receive the same twice successively.
One of the solutions for the above problem in the paging receiver is to use a so-called simulcasting through a kind of controlled line between the corresponding transmitters of associated base stations and paging terminals, which simulcasting functions to transmit a multiplicity of paging data simultaneously by making the starting times of data transmission in those transmitters having the same channel of data in the respective base stations coinside. This method of simulcasting of the paging data provides a better quality of paging service even for paging receivers located in those reiteration cells. U.S. Pat. No. 5,355,529 to Roger D. Linquist, et al., entitled Paging System With Satellite Time Base and U.S. Pat. No. 5,365,569 to Mark L. Witsaman, et al., Entitled Digital Simulcast Transmission System are two example of known simulcast systems and are incorporated